Embodiments herein generally relate to solid ink jet printing. More specifically, certain embodiments relate to the overcoating of images prepared by printing on a substrate with a solid ink.
Prints generated by solid ink jet printers are known to rub off and scratch due to poor bonding between the ink and substrate. This characteristic of solid ink jet prints can result in unsatisfactory prints and customer complaints. For example, in the packaging industry, images printed on packaging (e.g., corrugated substrates) using solid ink can be damaged and the ink can be transferred to other packages and cause contamination.
Compared to toner prints, there is very little pressure applied to ink during the solid ink jet printing process (in both transfix and direct to paper configurations). Due to the relatively low pressure applied during solid ink jet printing, diffusion of ink into the substrate is reduced and the resulting images can be sharper/crisper, as a result. However, in the final solid ink print image, the ink rests on top of the substrate and there is very little bonding between the ink and the substrate. In addition, the wax content of solid ink jet prints can be very high, resulting in an image that can remain soft after printing and can, thus, be easily damaged with only a small amount of force being applied to the print.
One approach to minimizing damage to printed images is to apply a coating over the image, thereby forming a protective barrier and increasing the robustness of the printed image. Aqueous overcoatings are known for improving surface properties (such as appearance, wear resistance and scratch resistance) of printed images on paper and plastic substrates, among others.
Providing a continuous dry film (overcoat) which has good adhesion to the surface of solid ink jet print images, as well as good scratch resistance, wear and fold properties would be beneficial, especially in the packaging industry. Further, it would be beneficial if such overcoats could also improve the aesthetic appeal of a solid ink image by increasing its gloss, among other aesthetic properties.